1. Field of the Invention
The present invention relates to a vehicle braking/driving force control apparatus for individually controlling a braking force or a driving force to be generated on each wheel of a vehicle.
2. Description of the Related Art
In recent years, as a form of an electric vehicle, there has been developed a vehicle of so-called in-wheel motor type including a motor arranged inside or in a neighborhood of a wheel and using the motor to directly drive the wheel. On the vehicle of in-wheel motor type, a driving force and a braking force of the vehicle can be controlled as appropriate depending on a travel condition of the vehicle by independently controlling rotation of the motor provided to each wheel (driving wheel), in other words, independently controlling power running or regeneration of each motor. There has been proposed a control apparatus for controlling a motion (behavior) generated on a vehicle and a body with use of capability of individual control of a driving force and a braking force on each driving wheel.
For example, Japanese Patent Application Laid-open No. 2012-86712 discloses a vehicle braking/driving force control apparatus capable of simultaneously controlling a plurality of behaviors (motions) generated on a vehicle. This related-art vehicle braking/driving force control apparatus calculates a target longitudinal driving force, a target roll moment, a target pitch moment, and a target yaw moment based on a driving operation state by a driver, a motion state of the vehicle, and the like. Then, the related-art vehicle braking/driving force control apparatus is configured to calculate and generate a driving force or a braking force to be distributed and generated on each wheel (each driving wheel) so as to simultaneously realize the calculated target longitudinal driving force, target roll moment, target pitch moment, and target yaw moment.
In this way, the related-art vehicle braking/driving force control apparatus can generate the driving force or the braking force distributed so as to simultaneously realize the target longitudinal driving force, the target roll moment, the target pitch moment, and the target yaw moment on each wheel (each driving wheel) to control the vehicle to appropriately travel, and can apply a reaction force generated by the driving force or the braking force on each suspension mechanism to a body, thereby, for example, simultaneously controlling a roll behavior, a pitch behavior, or a yaw behavior. As a result, as compared with the case of independently controlling the roll behavior, the pitch behavior, and the yaw behavior, the related-art braking/driving force control apparatus can effectively prevent the pieces of control for the respective behaviors from mutually influencing one another, and can thus control the vehicle to appropriately travel while suppressing a change in behavior of the body, thereby excellently securing ride comfort.
By the way, in the related-art vehicle braking/driving force control apparatus, each of all the wheels (all the driving wheels) generates the driving force or the braking force distributed so as to simultaneously realize the target longitudinal driving force, the target roll moment, the target pitch moment, and the target yaw moment, to thereby accelerate or decelerate the vehicle for appropriate travel while simultaneously controlling the roll behavior (roll motion), the pitch behavior (pitch motion), and the yaw behavior (yaw motion). Therefore, for example, when a slip occurs on at least one wheel among all the wheels (all the driving wheels), the driving force or the braking force distributed as described above cannot be generated on the wheel on which the slip is occurring. As a result, the target longitudinal driving force, the target roll moment, the target pitch moment, and the target yaw moment may be hard to be simultaneously realized. Thus, the attitude of the body is disturbed to decrease the ride comfort, and unintended acceleration/deceleration and a bias may occur in the vehicle.